Apologies for strayung off-topic slightly, but it's an interesting question just how much weight his rank carries. He's the ranking (Starfleet) officer of the station yes, but his actual rank was still only Commander until near the end of season 3. Would a visiting Captain be able to pull rank on Sisko? Would, say, Janeway technically outrank him?
I can only speculate that DS9 wasn't considered a significant post, and there was a desire to make it seem that Starfleet was sharing control with Bajorans.
On the other hand, I am surprised Sisko wasn't an admiral by the end of the series. He was heavily involved in strategy and diplomacy during the Dominion War.